Direct current (DC) to DC converters are widely used in electronic devices such as cellular phones and laptop computers, which are supplied with DC power, e.g., from batteries. Such electronic devices typically contain multiple sub-circuits, each of which is powered by a driving voltage different from the battery voltage. Additionally, some sub-circuits need different driving voltages in order to work in different operation modes. Take a central processing unit (CPU) in a sub-circuit, for example: a driving voltage for the CPU when the CPU is executing an instruction is higher than that when the CPU is idle.
The DC to DC converter is capable of converting the battery voltage to a regulated DC voltage which is suitable for driving a particular sub-circuit. FIG. 1 illustrates a block diagram of a conventional converter circuit 100. The converter circuit 100 includes a battery pack 110, a buck converter 120, and a controller 130. The battery pack 110 provides an input voltage VIN. The buck converter 120 includes switches 122 and 124, an inductor 126, and a capacitor 128, and is operable for converting the input voltage VIN to an output voltage VOUT. The controller 130 includes a regulator 132 for receiving a reference voltage VSET indicative of a desired voltage VDSR—1, e.g., VDSR—1 is suitable for driving a corresponding sub-circuit 140 coupled to the output of the buck converter 120, and for receiving a feedback signal 146 indicative of the output voltage VOUT. By comparing the feedback signal 146 to the reference voltage VSET, the regulator 132 provides switch-control signals 142 and 144 to turn on the switches 122 and 124 alternately. Accordingly, the level of the output voltage VOUT is maintained at the desired voltage VDSR—1.
However, when the reference voltage VSET is changed to a new level indicative of a desired voltage VDSR—2, the output voltage VOUT is not changed instantaneously to VDSR—2. Because the reference voltage VSET is different from the output voltage VOUT (e.g., VOUT is still equal to VDSR—1), a protection component 134 in the controller 130 will regard such a situation as an abnormal condition, e.g., an over-voltage or an under-voltage condition. As such, the protection component 134 generates a termination signal 138 indicating the abnormal condition. Accordingly, the regulator 132 controls the switch-control signals 142 and 144 to keep turning off the switch 122 and turning on the switch 124, which will terminate the operation of the buck converter 120.
Alternatively, the controller 130 does not include the protection component 134. In this instance, the controller 130 changes VOUT to VDSR—2 abruptly by adjusting the energy stored in the inductor 126 and the capacitor 128, which causes a sharp increase of a current through the components in the buck converter 120, e.g., the capacitor 128 and the inductor 126. Consequently, such components may be damaged and the lifetime of the converter circuit 100 may be shortened.